Chapter 8: Oxygen Demand. It is a measure of the amount of “reduced” organic and inorganic matter in a water Relates to oxygen consumption in a river or lake as a result of a pollution discharge Measured in several ways BOD - Biochemical Oxygen Demand COD - Chemical Oxygen Demand
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C6H12O6 + 6O2 = 6CO2 + 6H2O
= 1.06 O2 / Glucose
If glucose concentration is 360 mg/L THOD is
1.06 * 360 mg/L = 384 mg/L Oxygen
Briefly, the BOD test employs a bacterial seed to catalyze the oxidation of 300 mL of full-strength or diluted wastewater. The strength of the un-diluted wastewater is then determined from the dilution factor and the difference between the initial D.O. and the final D.O.
BottleBOD - loss of biodegradable organic matter (oxygen demand)
Lo-Lt = BODt
L or BOD remaining
L=oxidizable carbonaceous material remaining to be oxidized
"L" is modelled as a simple 1st order decay:
Which leads to:
And combining with:
2 moles oxygen/1 mole of ammonia
4.57 grams oxygen/gram ammonia-nitrogen
Inorganic NH3, NO3- NO2-
Organic Proteins, Amino acids
TKN = Ammonia-N + Organic Nitrogen
The chemical oxygen demand (COD) of a waste is measured in terms of the amount of potassium dichromate (K2Cr2O7) reduced by the sample during 2 hr of reflux in a medium of boiling, 50% H2SO4 and in the presence of a Ag2SO4 catalyst.